定义Definition
平面手性是由于取代基相对于一个平面（如环或芳环）的不对称排列，使得平面的两个面不等价、分子与镜像不能重合而产生的手性。典型例子是 1,2-二取代二茂铁、取代环芳烷和反式环辛烯。
Planar chirality arises when substituents are arranged unsymmetrically with respect to a plane (a ring or arene), making the two faces inequivalent and the molecule non-superimposable on its mirror image — e.g. 1,2-disubstituted ferrocenes, substituted cyclophanes and trans-cyclooctene.
例子Examples
带两个不同取代基的二茂铁（两个取代基在同一个 Cp 环上）；[2.2]对环芳烷衍生物；反式环辛烯（亚甲基链只能从双键平面一侧跨过，1962 年由科普拆分）。
Ferrocenes bearing two different substituents on one Cp ring; [2.2]paracyclophane derivatives; trans-cyclooctene (the chain spans one face of the alkene; resolved by Cope in 1962).
应用Applications
平面手性二茂铁膦配体（如 Josiphos，用于工业合成除草剂异丙甲草胺）在不对称氢化中极为重要。
Planar-chiral ferrocenyl phosphines (Josiphos, used industrially for the herbicide (S)-metolachlor) are vital in asymmetric hydrogenation.
标记Descriptors
按 CIP 规则选领航原子，从领航原子看平面上三个原子的排列顺序给出 Rₚ/Sₚ。
A pilot atom is chosen by CIP rules, and the sequence of three in-plane atoms seen from it gives Rp/Sp.
年表Timeline
- 1962
科普拆分反式环辛烯
Cope resolves trans-cyclooctene
- 1996
Josiphos 用于异丙甲草胺工业生产
Josiphos used for industrial (S)-metolachlor